Apex domains cannot have CNAME records.
Question and response
Question
dig cntech.net. NS
Answer
cntech.net. 4 NS us.hketc.net.
cntech.net. 4 NS ca.hketc.net.
cntech.net. 4 NS host2.cntech.net.
cntech.net. 4 NS host1.cntech.net.
Authority
The response has no authority records.
Additional
ca.hketc.net. 4 A 116.92.229.27
us.hketc.net. 4 A 202.155.202.114
host1.cntech.net. 4 A 157.245.195.0
host2.cntech.net. 4 A 139.162.27.162
host1.cntech.net. 4 AAAA 2400:6180:0:d0:0:0:132b:3001
host2.cntech.net. 4 AAAA 2400:8901:0:0:f03c:93ff:fe89:a03a
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0